单片机 bootloader 设计

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1、AN851AFLASHBootloaderforPIC16andPIC18DevicesAuthor:RossM.FoslerandFIGURE1:BOOTLOADERFUNCTIONALRodgerRicheyBLOCKDIAGRAMMicrochipTechnologyInc.BootloaderFirmwareRXTXINTRODUCTIONTransmit/ReceiveUSARTAmongthemanyfeaturesbuiltintoMicrochip’sEngineEnhanced

2、FLASHMicrocontrollerdevicesisthecapa-bilityoftheprogrammemorytoself-program.ThisveryusefulfeaturehasbeendeliberatelyincludedtogiveRAMBuffertheusertheabilitytoperformbootloadingoperations.DeviceslikethePIC18F452aredesignedwithadesig-FLASHControlnated“

3、bootblock”,asmallsectionofprotectablepro-ProgramgrammemoryallocatedspecificallyforbootloadMemoryfirmware.CommandDataBusEEDataInterpreterThisapplicationnotedemonstratesaverypowerfulMemorybootloaderimplementationforthePIC16F87XAandPIC18Ffamiliesofmicro

4、controllers.ThecodingfortheConfigurationRegisterstwodevicefamiliesisslightlydifferent;however,thefunctionalityisessentiallythesame.Thegoalsofthisimplementationstressamaximumperformanceandfunctionality,whilerequiringaminimumofcodespace.COMMUNICATIONSF

5、IRMWAREThemicrocontroller’sUSARTmoduleisusedtoreceiveandtransmitdata;itisconfiguredasaUARTtoBasicOperationbecompatiblewithRS-232communications.ThedevicecanbesetupinanapplicationtobootloadfromFigure1summarizestheessentialfirmwaredesignofacomputerthrou

6、ghitsstandardserialinterface.Thethebootloader.DataisreceivedthroughtheUSARTfollowingcommunicationssettingsareused:module,configuredinAsynchronousmodeforcompat-•8databitsibilitywithRS-232andpassedthroughthetransmit/receiveengine.Theenginefiltersandpar

7、ses•Noparitythedata,storingtheinformationintoadatabufferin•1STOPbitRAM.Thecommandinterpreterevaluatesthecom-Thebaudratesettingisvariabledependingonthemandinformationwithinthebuffertodeterminewhatapplication.Baudrateselectionisdiscussedlater.shouldbed

8、one(i.e.,Isthedatawrittenintoamemoryunit?Isdatareadfromamemoryunit?Doesthefirm-wareversionneedtoberead?).Oncetheoperationisperformed,dataispassedbacktothetransmit/receiveenginetobetransmittedbacktothesource,closingthesoftwareflowcontrolloop.
2002Micr